Sparking device



May 22, 1956 T. TOGNOLA 2,747,123

SPARKING DEVICE Filed Sept. 29, 1952 J INVENTOR.

Mb Jay/ fg, BY

ATTORNEY.

SPARKING DEVICE Tullio Tognola, Sidney, N. Y., assignor to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application September 29, 1952, Serial No. 311,969

7 Claims. (Cl. 313-131) This invention relates to electrical apparatus and more particularly to sparking devices such as spark plugs or igniter plugs for the ignition systems of engines.

One of the objects of the present invention is to provide a novel spark gap construction of the type presently known as the shunted surface gap type.

Another object of the invention is to provide a novelly constructed spark gap device of the type wherein the gap electrodes are bridged by a semi-conductor of high resistance or the like, whereby ionization of the gap may be effected at relatively low voltage.

Still another object is to provide a device of the above character wherein the structure is simple and yet sturdy and reliable.

A further object is to provide such a device which is novelly constructed to embody a minimum number of simple elements or parts which may be easily and quickly assembled and which are themselves of simple construction and easy to fabricate.

The above and further objects and novel features of the present invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a side elevation, partly in section and with parts broken away, showing one form of sparking device embodying the present invention, the section being taken substantially on line 1--1 of Fig. 2;

Fig. 2 is a bottom view of the device of Fig. 1; and

Fig. 3 is a sectional view taken substantially on line 3-3 of Fig. l.

The single embodiment of the invention illustrated in the drawings, by way of example, is in the form of a spark plug or igniter plug adapted for use in the ignition system of engines, including reciprocating, gas turbine, jet and other types. The structure shown is designed, primarily, for use in a system wherein sparks or arcs are created by the intermittent discharge of a condenser across the spaced electrodes of a spark gap, but the same may be used in other circuits wherein voltage pulses having relatively steep wave fronts are generated.

The form of sparking device shown in the drawing comprises an outer metallic shell 10, the lower end of which is partially closed by a transverse wall 11. The latter may be formed integrally with the shell or integrated therewith in any suitable known manner, such as by welding or silver soldering and is slotted in a manner hereinafter described to function as a ground or low potential electrode of a spark gap.

Within shell is an electrical insulator 12 which seats against the inner plane face of electrode wall 11 and may be secured in place by any of many well-known means for this purpose. Passing downwardly through the center of the insulator 12 and insulated thereby from shell 10 nited States Patent "ice 2,747,123 Patented May 22, 1956 is a conductor bar 14 which maybe connected in any suitable known manner to a source of electrical energy, such as to a storage condenser, magneto, or the like. Bar 14 terminates short of the lower end of insulator 12 and is connected by one or more wires 15 to an electrode 16 to be next described. The lower end of the central bore through insulator 12 may be filled with insulation 17 or left void.

The novel spark gap of the present invention comprises the metallic ring 16 which is embedded in an annular dove-tail groove in the lower end of insulator 12. Ring electrode 16 may be of any suitable electrode metal, such as silver, and may be cast or otherwise suitably embedded therein. The outer face of ring 16 is exposed through a shallow annular groove 18. Wall 11 has a beveled annu-' lar groove 19 in the outer face thereof, said groove being concentric with groove 18. A plurality of arcuate, circumferentially spaced slots 20 in end wall 11 register with groove 18 to form a plurality of spark gaps in conjunction with ring 16. The gaps which are thus formed between the face of ring 16 and the inner and outer arcuate walls of slots 20 are bridged by the cylindrical walls available voltage. To avoid any danger of sparks occ'urring beneath the webs 21 which connect the ends of slots 20, the inner or upper surfaces of said webs are countersunk to a depth of about .010 inch or more, as shown at 22.

In order to render the above described device operative at low voltages, the walls of groove 18 which bridge the spark gaps are rendered semi-conductive in any suitable known manner, such as by applying thereto a very thin layer of electrically conductive material, such as graphite, silver nitrate or the like. If desired, the device may be prepared for use in a low voltage circuit, i. e., voltages of about 2,000 volts or less, by pre-sparking at a voltage which will bridge the gap without assistance of pro-ionization. During the pre-sparking, a carbon deposit is left on the bridging surfaces, i. e., on the walls of groove 18. When the device is put into a combustion chamber, the carbon deposit or other conductive coating, as the case may be, is effective at relatively low voltage to conduct a small but suflicient amount of electrical energy to bring about ionization of the medium between the electrodes so that the low voltage impressed thereon, such as by a charged condenser, becomes capable of bridging the gap to produce a high energy spark.

There is thus provided a sparking device of the shunted gap type which is of simple construction and may be readily fabricated at low cost. The construction of the spark gap is such that considerable wear or erosion of the parts affected by the sparks or arcs will not materially affect the operation and operating efiiciency of the device. Additionally, a sturdy structure is provided wherein a large sparking area is made available by the novel construction and arrangement of the parts, thereby insuring a longer life and improved reliability.

Although only a single embodiment of the invention is illustrated in the drawings and a limited number of modifications are described in the foregoing specification, it is to be expressly understood that the invention is not limited thereto. For example, the invention may be embodied in many types of sparking devices other than shielded spark plugs and put to many uses other than engine ignition systems. The specific form of the ground electrode may be varied greatly, as for example, the beveled groove may be dispensed with and the slots may be differently shaped and arranged. Various other changes may also be made in the materials suggested for use and in the design and arrangement of parts illustrated without departing from the spirit and scope of the invention as will now be clear to those skilled in the art.

What is claimed is:

l. A sparking device comprising a tubular metallic shell, an electrode member extending across the end of said shell, an electrical insulator in the shell and seated on said member, and an annular electrode embedded in said insulator and having a surface thereof exposed by a shallow groove in the end face of said insulator, said electrode member having arcuate slots therethrough in substantial registry with said shallow groove, whereby the walls of said groove bridge spark gaps between the walls of said slots and the exposed surface of said annular electrode.

2. A sparking device as defined in claim 1 wherein said electrode member is integral with said shell.

3. A sparking device as defined in claim 1 wherein the webs of said electrode member between the ends of said slots have the faces thereof adjacent the insulator indented to enlarge the distance therefrom to the exposed surface of the annular electrode.

4. A sparking device comprising an insulator having an annular groove therein, an annular electrode partially filling said groove, means in said insulator for connecting said electrode to a source of electrical energy, and a second electrode in spark gap relation with said annular electrode at both the inner and outer peripheries of said groove, the gap being bridged by the peripheral walls of the unfilled portion of said groove.

5. A sparking device comprising an electrode member, an electrical insulator seated against said member, and an electrode embedded in said insulator and having a surface exposed toward said member through a shallow groove in said insulator, said electrode member having a slot therethrough in substantial registry with at least portions of the inner and outer peripheries of said groove.

6. A sparking device as defined in claim 5 comprising conductive means extending through the insulator and connected to said embedded electrode.

7. A spalking device comprising a tubular metallic shell, an electrode member extending across the end of said shell, an electrical insulator in the shell and seated on References Cited in the file of this patent UNITED STATES PATENTS Peters et al. Oct. 28, 1941 Smits Oct. 24, 1950 

